Leo Cullen has warned Leinster's young Ireland stars that a Grand Slam medal is no guarantee of a place in the Blues team for the big games at the business end of the season.

Five of Joe Schmidt's 'Magnificent Seven' who have yet to lose a match in Ireland colours are Leinster men, and all played a big part in the Slam-sealing success at Twickenham last Saturday, but they can't expect to waltz back into their province's UCD base and walk into the side to host Saracens in the European Champions Cup quarter-final on Sunday week.

"Exactly, yeah," said head coach Cullen. "We want to have a competitive group and we've worked hard to build the depth and bring young guys through.

"It makes it tough in terms of selection but it's positive because we want it to be competitive.

"We've used 52 players already this season, so it's a competitive group and all the players want to be involved in the big knockout games. You don't have to be a genius to figure out that 52 doesn't go into 23."

Of Leinster's five young Ireland hotshots, Joey Carbery, Jordan Larmour and Andrew Porter have been kept out of Joe Schmidt's starting XV by provincial team-mates Johnny Sexton, Rob Kearney and Tadhg Furlong, so can hardly expect to flip the pecking-order with the Blues, although there is a good chance Larmour will play on the wing against Saracens.

However, any demotion might seem strange for James Ryan and Dan Leavy, who were both on the field for most of Ireland's victorious Six Nations campaign. Yet second-row Ryan has only ever started two European games - both when Scott Fardy was unavailable - while flanker Leavy has started just one this season. And with Sean O'Brien recovering well from his latest injury, the No 7 jersey is up for grabs. "It's not beyond the realms of possibility Seanie will play next week," said Cullen, who welcomes back scrum-half Luke McGrath for Saturday's Guinness PRO14 trip to Ospreys.

However he resolves his selection conundrum, Cullen is not worried that any of his Six Nations champions will struggle to switch focus to provincial matters, and he does not feel he has to try to keep their feet on the ground. In fact, he is confident that the positivity brought back by the internationals can lift Leinster to similar heights, just as it did after the 2009 Grand Slam, when Leinster went on to win their first Heineken Cup.

"Guys who have been successful, if you win something you generally want to go out and do it again soon after because the feeling of Six Nations success is quite nice and people want to repeat those feelings again," said Cullen, who will reintroduce his Ireland fringe men - the likes of Carbery, Larmour, Porter, Sean Cronin and Jordi Murphy - in Swansea. Schmidt's starters will be given the weekend off to rest.

"Playing Ospreys away is a tough challenge. A lot of guys will be scrapping to put in a performance to try and get in the team for the following week. They know what's at stake, I think … well they should know at this stage."

Meanwhile, Robbie Henshaw provided a boost yesterday as he set his sights on a comeback in time for a potential European semi-final.

"I'll push it as hard and as fast as I can to get back," said the centre, who has used the five weeks since dislocating his shoulder against Italy to catch up on his Arts with economics and geography degree in UCD.